Tungsten Copper Heat Sink Material Hermeticity

Based on high density, high strength, excellent chemical stability and arc ablation resistance, tungsten copper material also has perfect thermal and electrical conductivity, which can be widely used in EDM electrodes, electrical contacts, military industry and heat sink materials. However, tungsten copper electrodes and contacts used for electrical machining has different requirements of properties with tungsten copper used in heat sink. As heat sink materials, tungsten copper not only be supposed to have excellent thermal conductivity, but also should have excellent hermeticity to ensure the equipment working stability. Since any porosity and leakage will lead to the operation failure of the microwave component.

In the early 1980s, tungsten copper has been chosen as heat sink materials, which due to it has the similar coefficient of thermal expansion to some ceramic, and both of them after brazing can not only guarantee the thermal matching, but also form a good thermal channel. Theoretically, W and Cu has big difference in physical and chemical properties, which the difference of melting point of them are as much as 2000℃. And they can not form a solid solution or a compound so that it is only suitable for using powder metallurgy process. And the best process is infiltration, tungsten powder is compacted to a certain density of blank, after sintering and shrinking at high temperature forms tungsten skeleton with a certain density and then at a temperature above the melting point of copper was infiltrated tungsten skeleton.

Since the high hardness and poor plasticity of tungsten powder, using a general manufacturing method infiltrated tungsten copper alloy will be some of the pores, the relative density can only reach about 60%. Densification at high temperatures also have some closing pores in copper infiltration process is not sufficiently filled with tungsten skeleton, reducing the product's tightness. In order to reduce the porosity of the relevant parameters need to be improved so that it can meet the requirement of hermeticity.